Method and Device for Producing Methanol

ABSTRACT

A method for producing methanol includes dissolving carbon dioxide in water to obtain a two-phase coexistence aqueous solution that is pressurized and heated to a critical state to separate critical state carbon dioxide and critical water. The critical state carbon dioxide is reduced to critical state carbon monoxide. The critical water is electrolyzed to obtain super critical state hydrogen and super critical state oxygen. The critical state carbon monoxide reacts with the super critical state hydrogen to produce methanol. Furthermore, a device for producing methanol is also provided in the present invention, comprising a mixing unit, a conversion unit and a synthesis unit, and which is highly effective in producing methanol and frugal in energy use.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and a device for producing methanol from biomass and, more particularly, to a method and a device for producing methanol with improved efficiency while consuming less energy.

2. Description of the Related Art

Conventionally, methanol is produced through chemical reconstitution, wherein methane is converted into methanol through use of a catalyst. However, the chemical reconstitution is slow in reactive efficiency. Thus, the conventional method can not fulfill the economic need.

Pursuant to continuing improvement in the converting techniques for converting bioenergy, the bioenergy conversion has been widely applied in various processes in the chemistry industries. Recovery of carbon dioxide emitted by the green house effect draws great attention. At the present stage, the carbon dioxide in the environment can be converted into methanol through burning, thermal chemical conversion, or biochemical conversion, seeking reduction in the consumed energy for producing methanol while recovering the environmental pollutant.

In Taiwan Patent No. 1230195 entitled “METHOD AND DEVICE FOR PRODUCING METHANOL FROM BIOMASS”, a biomass is gasified to generate a gas for producing methanol. The gas is carbon monoxide. Water is electrolyzed in a water-electrolyzing device by electricity obtained from a solar generator or wind generator to generate hydrogen and oxygen. When the amount of hydrogen is more than two times of that of the carbon monoxide, the hydrogen obtained from electrolysis is supplied to the gas, producing methanol in a methanol synthesis tower.

Conventionally, carbon monoxide directly reacts with gaseous hydrogen obtained from water electrolysis to form the methanol. However, the bond strength between the hydrogen atom and the oxygen atom of liquid water at normal temperature and normal pressure does not permit separation of the hydrogen atom from the oxygen atom. External strong current must be provided to electrolyze liquid water to obtain gaseous hydrogen and gaseous oxygen, which consumes considerable energy and requires a long period of time of electrolysis to release sufficient gaseous hydrogen. Thus, the yield of gaseous hydrogen is low, because it is obviously limited to the reaction time of water electrolysis. The production efficiency and yield of subsequently formed methanol are also adversely affected.

Furthermore, during the process of electrolyzing the liquid water into gaseous hydrogen and gaseous oxygen, only the gaseous hydrogen is used to react with carbon monoxide to obtain methanol. Namely, the oxygen is not effectively used, leading to a waste and failing to meet the goal of recovering energy.

Thus, a need exists for a method and a device for producing methanol with improved production efficiency while recovering energy.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a method for producing methanol by using gaseous hydrogen obtained from electrolyzing critical state liquid water that consumes less energy, effectively increasing the electrolyzing efficiency of the liquid water.

Another objective of the present invention is to provide a method for producing methanol for increasing the yield of gaseous hydrogen, effectively increasing the production efficiency of methanol.

A further objective of the present invention is to provide a device for producing methanol that reduces the energy consumed for producing the methanol, effective saving energy.

Still another objective of the present invention is to provide a device for producing methanol that can recover and store gaseous oxygen obtained from electrolyzing critical state liquid water to reuse energy.

The present invention fulfills the above objectives by providing, in an aspect, a method for producing methanol includes a pre-step, a conversion step, and a synthesis step. The pre-step includes dissolving carbon dioxide in water to obtain a two-phase coexistence aqueous solution. The conversion step includes: pressurizing and heating the two-phase coexistence aqueous solution to a critical state to separate critical state carbon dioxide and critical water, reducing the critical state carbon dioxide to critical state carbon monoxide, and electrolyzing the critical water to obtain super critical state hydrogen and super critical state oxygen. The synthesis step includes reacting the critical state carbon monoxide with the super critical state hydrogen to produce methanol.

Preferably, the two-phase coexistence aqueous solution in the critical state has a pressure of 221 atm and a temperature of 672K.

Preferably, the two-phase coexistence aqueous solution is pressurized and heated in the pre-step to turn the two-phase coexistence aqueous solution with carbon dioxide into a high temperature/high pressure state.

Preferably, the two-phase coexistence aqueous solution in the high temperature/high pressure state has a pressure of 20 atm and a temperature higher than 330K.

Preferably, the conversion step includes a separation step, a reduction step, and an electrolysis step. The critical state carbon monoxide and the super critical state hydrogen are obtained by the separation step, the reduction step, and the electrolysis step.

Preferably, the separation step includes separating high temperature/high pressure gaseous carbon dioxide and high temperature/high pressure liquid water from the two-phase coexistence aqueous solution.

Preferably, the reduction step includes reducing the high temperature/high pressure gaseous carbon dioxide in high temperature/high pressure gaseous carbon monoxide and then heating and pressurizing the high temperature/high pressure gaseous carbon monoxide into critical state carbon monoxide.

Preferably, the reduction step includes supplying an electric current of 10-20 A to generate the high temperature/high pressure gaseous carbon monoxide from the high temperature/high pressure carbon dioxide and then compressing the gaseous carbon monoxide at 30 atm and 400 k into the critical state carbon monoxide at 221 atm and 672K.

Preferably, the electrolysis step includes heating and pressurizing the high temperature/high pressure liquid water to the critical state to obtain the critical water and electrolyzing the critical water into the super critical state hydrogen and the super critical state oxygen.

Preferably, the high temperature/high pressure liquid water in the critical state has a pressure of 221 atm and a temperature of 672, and the super critical state hydrogen and the super critical state oxygen have a pressure of 230 atm and a temperature of 700K.

In another aspect, a device for producing methanol includes a mixing unit, a conversion unit, and a synthesis unit. The conversion unit is connected by a first pipe to the mixing unit. A first pressurizing member and a first heating member are mounted between the conversion unit and the mixing unit. The conversion unit outputs a critical state gas. The synthesis unit is connected by a second pipe to the conversion unit. The second pipe allows the critical state gas to flow into the synthesis unit. A gas outlet pipe is connected to the synthesis unit and outputs a synthetic gas in the synthetic unit.

Preferably, the conversion unit includes a separator, a reducer, and an electrolyser. The separator is connected to the reducer by a first branch pipe, and a second branch pipe is connected between the separator and the electrolyser.

Preferably, the synthesis unit is connected to the reducer and the electrolyser by first and second gas inlet pipes, respectively.

Preferably, a second pressurizing member and a second heating member are mounted on the second branch pipe, and a third pressurizing member and a third heating member are mounted on the first gas inlet pipe connected between the reducer and the synthesis unit.

Preferably, the reducer is connected to a current supplier that supplies the reducer with electric current.

Preferably, the electrolyser is connected to a current supplier that supplies the electrolyser with electric current.

Preferably, the electrolyser is connected to a storage tank by a gas conveying pipe.

Preferably, a plurality of heat dissipating members is mounted between the electrolyser and the storage tank.

Preferably, the separator further includes an auxiliary heating member for heating the separator.

The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The illustrative embodiments may best be described by reference to the accompanying drawings where:

FIG. 1 shows a flowchart illustrating a method for producing methanol according to the present invention.

FIG. 2 shows a flowchart illustrating a preferred embodiment of the method for producing methanol according to the present invention.

FIG. 3 shows a schematic diagram of a device for producing methanol of an embodiment according to the present invention.

FIG. 4 shows a schematic diagram of a device for producing methanol of another embodiment according to the present invention.

All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiments will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a method for producing methanol according to the present invention includes a pre-step S1, a conversion step S2, and a synthesis step S3.

In the pre-step S1, carbon dioxide in the environment dissolves in water to obtain two-phase coexistence aqueous solution with carbon dioxide. The two-phase coexistence aqueous solution is heated and pressurized to the critical state in the conversion step S2, obtaining critical state carbon dioxide and critical water. The critical state carbon dioxide is reduced to critical carbon monoxide. The critical water is electrolyzed to obtain super critical state hydrogen and super critical state oxygen. In the synthesis step S3, the critical state carbon monoxide reacts with the super critical state hydrogen to obtain methanol. Since the aqueous solution can be rapidly heated and pressurized, when the two-phase coexistence aqueous solution reaches the critical state, gaseous hydrogen can be obtained by critical state water electrolysis that consumes less energy. The electrolysis efficiency of liquid water is effectively increased to increase the production efficiency and yield of methanol.

By use of the two-phase coexistence aqueous solution that can rapidly reach the critical state, the present invention can obtain super critical state hydrogen and super critical state oxygen from water electrolysis that consumes less energy. To achieve better effect of less energy consumption, the present invention uses multiple-stage heating and pressurization which will is described hereinafter. It can be appreciated by one skilled in the art that the embodiment is illustrative rather than restrictive.

FIG. 2 shows a preferred embodiment of the method for producing methanol according to the present invention. Specifically, the method for producing methanol includes a pre-step S1, a conversion step S2, and a synthesis step S3.

In the pre-step S1, carbon dioxide in the environment dissolves in water, and the two-phase coexistence aqueous solution with carbon dioxide turns into a high temperature/high pressure state. Specifically, the carbon dioxide can be an air pollutant containing carbon in the environment. The gaseous carbon dioxide in the air dissolves in liquid water to obtain the two-phase coexistence aqueous solution with carbon dioxide (see chemical equation 1 below).

CO_(2(g,T1))+H₂O_((λ,T1))→CO_(2(aq,T1))  (1)

wherein T1=298K, and P=1 atm.

Preferably, the two-phase coexistence aqueous solution is pressurized at a normal temperature. The two-phase coexistence aqueous solution turns into a high pressure state when its pressure is above 1 atm. Then, the high pressure state two-phase coexistence aqueous solution is heated to a high temperature, turning the two-phase coexistence aqueous solution into a high temperature/high pressure state (see chemical equation 2 below).

CO_(2(aq,T1,P1))→CO_(2(aq,T2,P2))  (2)

wherein T1=298K, P=1 atm, T2=400K, and P2=20 atm.

The term “normal temperature” referred to herein means 298K, which can be appreciated by one skilled in the art. The term “high temperature” referred to herein means a temperature higher than the normal temperature. The term “normal pressure” referred to herein means 1 atm, which can be appreciated by one skilled in the art. The term “high pressure” referred to herein means a pressure higher than the normal pressure.

As an example, in this embodiment, gaseous carbon dioxide at 1 atm and 298K dissolves in liquid water at 1 atm and 298K to obtain two-phase coexistence aqueous solution at 1 atm and 298K. The two-phase coexistence aqueous solution at 1 atm and 298K is pressurized by a pump to 20 atm and 330K. The two-phase coexistence aqueous solution is then gradually heated to 400K.

The conversion step S2 includes a separation step S21, a reduction step S22, and an electrolysis step S23. Through the three steps S1, S2, and S3, the two-phase coexistence aqueous solution is heated and pressurized to the critical state, obtaining critical state carbon monoxide and super critical state hydrogen.

Specifically, in the separation step S21, the two-phase coexistence aqueous solution with carbon dioxide is heated to the critical state where gas separates from liquid. Thus, gaseous carbon dioxide and liquid water are separated from the two-phase coexistence aqueous solution and are maintained in a high temperature/high pressure state (see chemical equation 3 below).

CO_(2(aq,T2,P2))→CO_(2(g,T2,P2))+H₂O_((λ,T2,P2))  (3)

wherein T2=400K, and P2=20 atm.

After producing high temperature/high pressure gaseous carbon dioxide in the separation step S21, the high temperature/high pressure gaseous carbon dioxide is supplied with electric current (preferably alternating current) and passes through a heterophase catalyst (such as an oxide containing nickel, ruthenium or titanium) in the reduction step S22. A reduction reaction is, thus, undergone to obtain high temperature/high pressure gaseous carbon monoxide. The high temperature/high pressure gaseous carbon monoxide is then heated and pressurized to produce critical state carbon monoxide (see chemical equations 4a and 4b below).

2CO_(2(g,T2,P2))→2CO_((g,T2,P3))+O_(2(g,T2,P3))  (4a)

2CO_((g,T2,P3))→2CO_((g,T3,P3))  (4b)

wherein T2=400K, P3=30 atm, T3=672K, and P3=221 atm.

In the electrolysis step S23, the high temperature/high pressure liquid water is firstly pressurized and then heated to increase the pressure and temperature such that the high temperature/high pressure liquid water immediately turns into critical water after reaching the critical state. At this time, the bond strength of the hydrogen bond of the critical water molecule is significantly lower than that of the water molecule at normal temperature/normal pressure. Thus, under low-current electrolysis, the bond-dissociation energy of the critical water molecule can be rapidly reached. As a result, the hydrogen molecules and oxygen molecules in the critical water can easily be separated, producing super critical state hydrogen and super critical state oxygen (see chemical equations 5a and 5b below).

2H₂O_((λ,T2,P2))→2H₂O_((λ,T3,P3))  (5a)

2H₂O_((λ,T3,P3))→2H_(2(g,T4,P4))+O_(2(g,T4,P4))  (5b)

wherein T3=672K, P3=221 atm, T4=700K, and P4=230 atm.

As an example, in this embodiment, the two-phase coexistence aqueous solution at 20 atm and 400K is heated to 221 atm and 672K such that super critical state carbon dioxide and water can be produced from the two-phase coexistence aqueous solution. The pressure and temperature of the gaseous carbon dioxide are 20 atm and 400K, respectively. The pressure and temperature of the liquid water are 20 atm and 400K, respectively. Next, alternating current of 10-20 A is supplied to reduce the gaseous carbon dioxide at 20 atm and 400K to gaseous carbon monoxide at 30 atm and 400K. A pump is used to heat and pressurize the gaseous carbon monoxide at 30 atm and 400K into critical state carbon monoxide (at 221 atm and 672K) that serves as one material for subsequent synthesis of methanol.

On the other hand, a pump is used to compress liquid water at 20 atm and 400K into liquid water at 221 atm. The liquid water at 221 atm is gradually heated to 672K and turns into critical water. Electric current is supplied to undergo electrolysis. After reaching the bond-dissociation energy of the critical water, super critical state hydrogen and super critical state oxygen can be separated from the critical water. The hydrogen and oxygen are maintained in the super critical state at 230 atm and 700K. The super critical state hydrogen serves as another material for subsequent synthesis of methanol. The super critical state oxygen can be recovered and stored for use in other industrial processes.

In the recovery step S3, the critical state carbon monoxide and the super critical state hydrogen undergo a synthetic reaction to produce gaseous methanol (see chemical equation 6 below). Specifically, in this embodiment, the critical state carbon monoxide at 221 atm and 672K reacts with the super critical state gaseous hydrogen at 230 atm and 700K to produce gaseous methanol after complete synthesis.

CO_((g,T3,P3))+2H_(2(g,T4,P4))→CH₃OH_((g,T5,P5))  (6)

wherein T5=730K, and P5=77 atm.

As mentioned above, in the method for producing methanol according to the present invention, after dissolving gaseous carbon dioxide in liquid water, the two-phase coexistence aqueous solution can easily be pressurized and heated due to tighter molecular alignment between liquid molecules than that between gaseous molecules. Furthermore, after separation of gas from liquid, the gaseous carbon dioxide can be reduced to gaseous carbon monoxide under the action of alternating current, and the gaseous carbon monoxide is heated and pressurized to turn into critical state carbon monoxide. At the same time, the liquid water rapidly turns into critical water under the second-time heating and pressurization to reduce the bond strength between the hydrogen atom and the oxygen atm. Thus, the bond-dissociation energy of hydrogen molecules and oxygen molecules can easily be reached by electrolysis, rapidly separating super critical state hydrogen and super critical state oxygen from the critical water. Thus, the production efficiency of super critical state hydrogen is increased, and the critical state carbon monoxide reacts with the super critical state hydrogen to produce methanol. As a result, the method for producing methanol according to the present invention increases the production efficiency of super critical state hydrogen from electrolyzing water by using the critical state while increasing the yield of super critical state hydrogen in a short period of time. Through reaction of a large amount of super critical state hydrogen and critical state carbon monoxide, the production efficiency and yield of methanol can be increased.

FIG. 3 shows a device for producing methanol, which is a preferred embodiment for producing methanol according to the present invention for more particularly illustrating the method for producing the methanol according to the present invention.

The device for producing methanol includes a mixing unit 1, a conversion unit 2, and a synthesis unit 3. The units 1, 2, and 3 are connected by different pipes to form a continuous passage of the device for producing methanol, which is described in detail as follows.

The mixing unit 1 is used to mix the reactant materials to assure that the reactant materials can flow into subsequent pipes in a liquid state. In this embodiment, the mixing unit 1 is a cooling/absorbing tower to assure that the carbon dioxide entering the mixing unit 1 can completely dissolve in liquid water to save the energy consumed in subsequent pressurization and heating.

The conversion unit 2 is connected by a pipe T1 to the mixing unit 1. At least one pressurizing member P and at least one heating member H are provided between the conversion unit 2 and the mixing unit 1. The conversion unit 2 is used to output critical gas. The pressurizing member P is used to compress the two-phase coexistence aqueous solution flowing through the pipe T1. The heating member H is connected to the pressurizing member P through the pipe T1 to heat the two-phase coexistence aqueous solution flowing from the mixing unit 1 through the pipe T1, turning the two-phase coexistence aqueous solution into a high temperature/high pressure state (even nearly the critical state) before entering the conversion unit 2.

The conversion unit 2 includes a separator 21, a reducer 22, and an electrolyser 23. The separator 21 is connected by the pipe T1 to the mixing unit 1 to receive the two-phase coexistence aqueous solution flowing through the pipe T1, separating and outputting gaseous carbon dioxide and liquid water. The separator 21 is connected by a first branch pipe T21 to the reducer 22, allowing flowing of the gaseous carbon dioxide from the separator 21. A second branch pipe T22 is connected between the electrolyser 23 and the separator 21 to introduce the liquid water flowing through the second branch pipe T22 into the electrolyser 23. The electrolyser 23 dissociates hydrogen and oxygen from the critical water and separately outputs super critical state hydrogen and super critical state oxygen. The two-phase coexistence aqueous solution is obtained by dissolving carbon dioxide in water. The pressurizing member P is preferably a pump.

The synthesis unit 3 is connected by another pipe to the conversion unit 2, allowing a critical state gas to flow into the synthesis unit 3. The synthesis unit 3 is connected to a gas outlet pipe T30 for outputting a synthetic gas from the synthesis unit 3. Specifically, the synthesis unit 3 is connected to the reducer 22 and the electrolyser 23 by two gas inlet pipes T31 and T32, respectively. The gas inlet pipe T31 allows flow of gaseous carbon monoxide from the reducer 22. The gas inlet pipe T32 allows flow of super critical state hydrogen from the electrolyser 23. The two gas inlet pipes T31 and T32 meet at the synthesis unit 3 to allow synthesis of critical state carbon monoxide and super critical state hydrogen to produce gaseous methanol that is outputted through the gas outlet pipe T30.

FIG. 4 shows another embodiment of the present invention using multiple-stage heating/pressurization. With reference to FIG. 4, another pressurizing member P1 and another heating member H1 are provided on the second branch pipe T22. A further pressurizing member P2 and a further heating member H2 are provided on the gas inlet pipe T31.

By providing the pressurizing member P and the heating member H on the pipe T1, the two-phase coexistence aqueous solution flowing from the mixing unit 1 through the pipe T1 can be turned into a high temperature/high pressure state so that the two-phase coexistence aqueous solution can carry high heat energy into the separator 21. At this time, the separator 21 receives the high temperature/high pressure two-phase coexistence aqueous solution. Furthermore, the separator 21 includes an auxiliary heating member 211 to provide the two-phase coexistence aqueous solution with more heat energy to assure that the high temperature/high pressure two-phase coexistence aqueous solution can reach the temperature allowing separation of gas and liquid in the separator 21. Thus, the separator 21 outputs gaseous carbon dioxide and liquid water. The detailed structure and operational principle of separation of gas and liquid of the separator 21 are known to one skilled in the art and are, thus, not described in detail to avoid redundancy.

Furthermore, a gas collector (not shown) can be provided above the separator 21 in this embodiment to absorb the gaseous carbon dioxide. The gaseous carbon dioxide is guided by the first branch pipe T21 into the reducer 22. The reducer 22 further connects to a current supplier 221 that preferably supplies the reducer 22 with sufficient alternating current to reduce the gaseous carbon dioxide in the reducer 22 in gaseous carbon monoxide.

Furthermore, the electrolyser 23 in this embodiment is connected by the second branch pipe T22 to the separator 21, and the pressurizing member P1 connected to the electrolyser 23 compresses the liquid water flowing from the separator 21 through the second branch pipe T22 so that the liquid water can reach the critical pressure value. The pressurizing member P1 is preferably a pump merely for increasing the pressure of the liquid water while maintaining the temperature of the liquid water. The heating member H1 connected to the electrolyser 23 heats the liquid water to the critical temperature value so that the liquid water turns into critical water and flows into the electrolyser 23. At this time, the electrolyser 23 is supplied with suitable current by another current supplier 231 to reach the electrolysis energy level of the critical water. By this arrangement, hydrogen molecules and oxygen molecules are dissociated by the electrolyser 23 from the critical water to respectively output super critical state hydrogen and super critical state oxygen. The detailed structure and operational principle of electrolysis of the electrolyser 23 are known to one skilled in the art and are, thus, not described in detail to avoid redundancy.

In this embodiment, by provision of the pressurizing member P2 and the heating member H2 on the gas inlet pipe T31, the synthesis unit 3 can turn the gaseous carbon monoxide flowing through the gas inlet pipe T31 into critical state carbon monoxide. Thus, the critical state carbon monoxide and the super critical state hydrogen can react in the synthesis unit 3 to produce gaseous methanol that is outputted via the gas outlet pipe T30 and that can serve as fuel in industrial processes.

Furthermore, the electrolyser 23 can be connected by a gas conveying pipe T23 to a storage tank 4 so that the super critical state oxygen from the electrolyser 23 can be conveyed to and stored in the storage tank 4 for other industrial processes. Further, a plurality of heat dissipating members (not shown) can be mounted between the electrolyser 23 and the storage tank 4 to achieve energy saving effect.

The method for producing methanol according to the present invention can be used on the device for producing methanol according to the present invention with simple connection equipment to increase the production efficiency of super critical state hydrogen by electrolysis of liquid water. Furthermore, through reaction of a large amount of super critical state hydrogen with critical state carbon monoxide, the production efficiency and yield of methanol can be increased. Further, the device for producing methanol according to the present invention can reduce the energy loss during the process. Further, the gaseous oxygen not used in the reaction can be recovered and stored, further saving and reusing energy.

In the method for producing methanol according to the present invention, by using gaseous hydrogen obtained from electrolyzing critical state liquid water that consumes less energy, the electrolyzing efficiency of the liquid water can easily be enhanced.

In the method for producing methanol according to the present invention, the yield of gaseous hydrogen can be increased to effectively increase the production efficiency of methanol.

In the device for producing methanol according to the present invention, the energy consumed for producing the methanol is reduced to effectively save energy.

In the device for producing methanol according to the present invention, gaseous oxygen obtained from electrolyzing critical state liquid water can be recovered and stored to reuse energy.

Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein. 

1. A method for producing methanol comprising: a pre-step including dissolving carbon dioxide in water to obtain a two-phase coexistence aqueous solution; a conversion step including: pressurizing and heating the two-phase coexistence aqueous solution to a critical state to separate critical state carbon dioxide and critical water from the two-phase coexistence aqueous solution, reducing the critical state carbon dioxide to critical state carbon monoxide, and electrolyzing the critical water to obtain super critical state hydrogen and super critical state oxygen; and a synthesis step including reacting the critical state carbon monoxide with the super critical state hydrogen to produce methanol.
 2. The method for producing methanol as claimed in claim 1, with the two-phase coexistence aqueous solution in the critical state having a pressure of 221 atm and a temperature of 672K.
 3. The method for producing methanol as claimed in claim 1, with the two-phase coexistence aqueous solution being pressurized and heated in the pre-step to turn the two-phase coexistence aqueous solution with carbon dioxide into a high temperature/high pressure state.
 4. The method for producing methanol as claimed in claim 3, with the two-phase coexistence aqueous solution in the high temperature/high pressure state having a pressure of 20 atm and a temperature higher than 330K.
 5. The method for producing methanol as claimed in claim 3, with the conversion step including a separation step, a reduction step, and an electrolysis step, with the critical state carbon monoxide and the super critical state hydrogen being obtained by the separation step, the reduction step, and the electrolysis step.
 6. The method for producing methanol as claimed in claim 5, with the separation step including separating high temperature/high pressure gaseous carbon dioxide and high temperature/high pressure liquid water from the two-phase coexistence aqueous solution.
 7. The method for producing methanol as claimed in claim 5, with the reduction step including reducing the high temperature/high pressure gaseous carbon dioxide in high temperature/high pressure gaseous carbon monoxide and then heating and pressurizing the high temperature/high pressure gaseous carbon monoxide into critical state carbon monoxide.
 8. The method for producing methanol as claimed in claim 7, with the reduction step including supplying an electric current of 10-20 A to generate the high temperature/high pressure gaseous carbon monoxide from the high temperature/high pressure carbon dioxide and then compressing the gaseous carbon monoxide at 30 atm and 400 k into the critical state carbon monoxide at 221 atm and 672K.
 9. The method for producing methanol as claimed in claim 5, with the electrolysis step including heating and pressurizing the high temperature/high pressure liquid water to the critical state to obtain the critical water and electrolyzing the critical water into the super critical state hydrogen and the super critical state oxygen.
 10. The method for producing methanol as claimed in claim 9, with the high temperature/high pressure liquid water in the critical state having a pressure of 221 atm and a temperature of 672, with the super critical state hydrogen and the super critical state oxygen having a pressure of 230 atm and a temperature of 700K.
 11. A device for producing methanol comprising: a mixing unit; a conversion unit connected by a first pipe to the mixing unit, with a first pressurizing member and a first heating member mounted between the conversion unit and the mixing unit, with the conversion unit outputting a critical state gas; and a synthesis unit connected by a second pipe to the conversion unit, with the second pipe allowing the critical state gas to flow into the synthesis unit, with a gas outlet pipe connected to the synthesis unit, with the gas outlet pipe outputting a synthetic gas in the synthetic unit.
 12. The device for producing methanol as claimed in claim 11, with the conversion unit including a separator, a reducer, and an electrolyser, with the separator connected to the reducer by a first branch pipe, with a second branch pipe connected between the separator and the electrolyser.
 13. The device for producing methanol as claimed in claim 12, with the synthesis unit connected to the reducer and the electrolyser by first and second gas inlet pipes, respectively.
 14. The device for producing methanol as claimed in claim 13, further comprising: a second pressurizing member and a second heating member mounted on the second branch pipe; and a third pressurizing member and a third heating member mounted on the first gas inlet pipe connected between the reducer and the synthesis unit.
 15. The device for producing methanol as claimed in claim 12, with the reducer connected to a current supplier, with the current supplier supplying the reducer with electric current.
 16. The device for producing methanol as claimed in claim 12, with the electrolyser connected to a current supplier, with the current supplier supplying the electrolyser with electric current.
 17. The device for producing methanol as claimed in claim 12, with the electrolyser connected to a storage tank by a gas conveying pipe.
 18. The device for producing methanol as claimed in claim 17, with a plurality of heat dissipating members mounted between the electrolyser and the storage tank.
 19. The device for producing methanol as claimed in claim 12, with the separator further including an auxiliary heating member, with the auxiliary heating member heating the separator. 